A horizontal axis windmill has the disadvantage that the vane assembly needs to be oriented into the wind and thus in an area subject to gusting and changing wind direction, the need to reorient the vane assembly to accommodate a change in wind direction will result in lost output. However, a vertical axis windmill does not need to have its vane assembly oriented into the wind and will respond to wind pressure regardless of wind direction.
Various vertical-axis windmills are known such as the Savonius which has a low efficiency and the Darious which has the disadvantage of not being a self-starting windmill. In the Panemone vertical-axis windmill, a number of paddles are hinged in a vertical direction to lever arms which in turn are free to move in a horizontal plane around a vertical axial rod. The paddles are hinged to the lever arms in such a manner that if the wind blows in one direction, each lifts against the wind presenting only its edge to the wind. If, however, the wind blows in the opposite direction, the paddle remains in a vertical position and the paddle moves in a horizontal plane under the force of the wind. Thus, for half a revolution, each paddle is being raised until only its edge is presented to the wind and for the other half of the revolution, each paddle falls until its full surface is presented to the wind. The advantage of this windmill is that it will respond to all wind directions but it rotates only at a low speed.
The invention aims to provide a vertical axis windmill which will rotate at a higher speed and/or give more driving force for the same wind speed.